New French president Emmanuel Macron appeared to have hit it off with Angela Merkel and welcomed a “profound revolution” in their cooperation when the German Chancellor gave her support for plans to develop a European fighter jet in Paris.

The pair have discussed plans to boost French and German language training in each other’s countries and Mrs Merkel was quick to back Mr Macron’s calls for deeper eurozone integration just a year after dismissing similar proposals from his predecessor Francois Hollande.

But there are still a number of issues that could bring the love-in to a juddering halt at any time.

Alongside US president Donald Trump, Mr Macron is a frequent critic of Germany’s trade and current account surplus, which he has described as “unacceptable.”

He wants Germany to start diverting its surpluses towards cash-strapped southern Europe but Berlin finance minister Wolfgang Schaüble told Der Spiegel any such move was unlikely as it would have to be approved by German voters.

Germany’s lack of spending on defence and reluctance to engage in dangerous combat operations, is another area of profound divergence.

Mr Macron said he could not force Germany to boost defence spending but said it was “naïve” to keep sheltering under “someone else’s umbrella”.

Tensions are building after Mr Macron hosted Mr Trump in a bid to strengthen relations between France and America.

Mr Macron has pledged to overhaul France’s employment rules by the end of September but German doubts about France and its ability to conduct unpopular reforms has not gone away despite the the new administration’s promises.

Mr Schaüble said Germany was in no rush to grant France a clean bill of health on its economy which blighted by high unemployment, weak growth and heavy debt.

Another source of tension is the battle for control of the European Central Bank.

The reign of Mario Draghi comes to an end in 2019 and the ECB job is on wish lists in Berlin and Paris.

France has not begun public jockeying for the position but control over the ECB is sure to loom powerfully as a subject of debate between the two capitals.